Developing agent recycling apparatus and image forming apparatus with the same apparatus

Abstract: A developing agent recycling apparatus (17), comprising recycling means for recycling a developing agent from a mixture of the developing agent and foreign substances, the recycling means having an attracting member (19) for attracting the developing agent and a filter (20) for preventing other materials than the developing agent of the mixture from passing, the filter (20) being disposed in a region that the developing agent is moved by the attracting member. The attracting member is disposed upstream of the filter in a gravity working direction so that the other materials, like paper dust, can drop by their own weight. Additionally there is disclosed a way of changing the magnet configuration of such a system when it is not used.

Description: The present invention relates to a developing agent recycling device for recycling a developing agent from mixture of the developing agent and foreign substances and an image forming apparatus comprising the developing agent recycling device. US 4,389,968 describes a toner regenerating device with a mesh disposed in the route of toner collected from an image bearing member, and an apparatus for imparting to the collected toner through the mesh a force causing the collected toner to pass through the mesh and a force causing the collected toner to move along to mesh and in which the collected toner on the mesh containing foreign matter and solidified toner is loosened so that a solidified toner is divided into fine particles while, at the same time, the foreign matter is caused to float up over the collected toner and prevented from passing through the mesh. US 4,601,569 discloses a cleaning apparatus including a magnetic cleaning brush for removing residual toner from a photoconductor. After a developing agent is transferred from an image carrier to a recording member, the residue that resides on the image carrier is usually removed by a cleaning blade or the like and then disposed of as waste substances. From resource recycling point of view, a developing agent recycling apparatus that separates a developing agent from the residue, an apparatus that uses the recycled developing agent, and the similar apparatuses have been proposed. In particular, various simple construction types of developing agent recycling apparatuses with a mesh-shaped filter that allows only a developing agent to pass and separates it from other foreign substances have been proposed. However, when a developing agent is separated from other foreign substances by using a filter, in particular, a mesh-shaped filter, the mesh of the filter will be clogged with foreign substances such as paper powder. When small foreign substances are removed, small mesh is used for the filter. However, in this case, the filter tends to be clogged. Thus, since the recycling apparatus should be frequently maintained, it is difficult to practically use the apparatus. The present invention has been made from the above-mentioned point of view. An object of the present invention is to provide a developing agent recycling device that prevents a filter from being clogged and to prolong maintenance intervals of the apparatus and an image forming apparatus with the developing agent recycling device. This object is achieved as for the device by the features of claim 1 and as for the apparatus by the features of claim 5. The invention is further developed by the features mentioned in the subclaims. These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings. Fig. 1 is a sectional view schematically showing an image forming apparatus according to the present invention; Fig. 2 is a sectional view showing a construction of the developing agent recycling apparatus; Fig. 3 is a side view showing the developing agent recycling apparatus; Fig. 4 is a sectional view showing a developing agent that is separated from non-magnetic substances (foreign substances) by the developing agent recycling apparatus; Fig. 5 is a sectional view showing a developing agent recycling apparatus according to a second embodiment of the present invention; Fig. 6 is a sectional view showing an image forming apparatus according to a third embodiment of the present invention; Fig. 7 is a sectional view showing a developing agent recycling apparatus according to the third embodiment of the present invention; Fig. 8 is a perspective view showing a mesh filter vibrating unit; Fig. 9 is a graph for explaining vibrations and toner passing efficiency; Fig. 10 is a graph for explaining variations of toner passing efficiency corresponding to presence and absence of vibrations; Fig. 11 is a sectional view schematically showing a developing agent recycling apparatus according to a fourth embodiment of the present invention; Fig. 12 is a sectional view showing a modification of the developing agent recycling apparatus according to the fourth embodiment; Fig. 13 is a sectional view schematically showing a developing agent recycling apparatus according to a fifth embodiment of the present invention; Fig. 14 is a graph for explaining variations of toner passing efficiency corresponding to presence and absence of a blade; Fig. 15 is a sectional view schematically showing a developing agent recycling apparatus according to a sixth embodiment of the present invention; Fig. 16 is an enlarged perspective view showing a residue layer restricting blade for use in a developing agent recycling apparatus according to a seventh embodiment of the present invention; Fig. 17 is a sectional view showing a construction of a magnetic pole position changing mechanism for use in a developing agent recycling apparatus according to an eighth embodiment of the present invention; Fig. 18 is a sectional view showing a construction of a magnetic pole position changing mechanism for use in the developing agent recycling apparatus according to the eighth embodiment of the present invention; Fig. 19 is a sectional view showing a construction of the developing agent recycling apparatus according to the eighth embodiment of the present invention; Fig. 20 is a sectional view showing a construction of a developing agent recycling apparatus according to a ninth embodiment of the present invention; Fig. 21 is a sectional view showing a construction of a magnetic pole position changing mechanism according to the ninth embodiment of the present invention; Fig. 22 is a sectional view showing a construction of a magnetic pole position changing mechanism according to the ninth embodiment of the present invention; and Fig. 23 is a block diagram showing a control system according to the ninth embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 is a sectional view schematically showing an image forming apparatus according to the present invention. Fig. 2 is a sectional view showing a construction of a developing agent recycling apparatus that separates a developing agent from a residue removed from an image carrier. Fig. 3 is a side view showing the developing agent recycling apparatus viewed from arrow A of Fig. 2. Fig. 4 is a sectional view of the developing agent recycling apparatus that separates a magnetic toner from non-magnetic substances (foreign substances). Next, an image forming process of the image forming apparatus will be described. A photosensitive member (image carrier or image bearing member) 1 that is rotated is equally charged by a charger 7. The photosensitive member 1 is exposed (by an optical system 8) with rays 8a corresponding to an image of an original document placed on a document table 9. Thus, a static latent image is formed. The latent image is visualized by a developing unit 2 with a single component developing agent composed of a magnetic toner. The toner image formed on the photosensitive member 1 is transferred to a recording member P by a transfer charger 4. The recording member P having the toner image is conveyed to a fixing unit 12 by a conveying belt 11. The fixing unit 12 fixes the toner image on the recording member P. Thereafter, the recording member P is unloaded to a paper output tray 13. After the toner image is transferred, a residual toner, paper powder, and the like reside on the photosensitive member 1. The residue is removed by a cleaning unit 5. Thereafter, the photosensitive member 1 is exposed with rays radiated from the exposing unit 6 and thereby the photosensitive member 1 is discharged. Thus, the next image forming process is prepared. The image forming apparatus shown in Fig. 1 removes foreign substances such as paper powder from the residue cleaned. Only the residual toner (magnetic toner) is conveyed to a hopper 3 of the developing unit 2 and reused. Next, with reference to Figs. 2 to 4, a developing agent recycling apparatus according to a first embodiment of the present invention will be described. The developing agent recycling apparatus comprises a frame 17, a rear end portion (hatched portion of Fig. 3) of a conveying path 24 having a conveying screw 24', a sleeve 18 that holds the residue and rotates in the direction of arrow C, a magnet 18' fixed in the sleeve 18 (so that S pole always faces upward as shown in Fig. 2), a restricting member 25 that restricts the thickness of the layer of the residue held on the sleeve 18, a sleeve 19 that attracts a toner from the sleeve 18 (the sleeve 19 rotates in the direction of arrow B), a magnet 19' (attracting member) fixed in the sleeve 19 (so that N pole always faces downward as shown in Fig. 2), a scrape-off blade 26 that scrapes off the toner from the sleeve 19, a forward end portion of a conveying path 27 having a conveying screw 27' that conveys the scraped toner to a developing hopper, a mesh-shaped filter (composed of non-magnetic stainless steel lines, non-magnetic brass lines, nylon fibers, or the like) 20, and a sealing member 30 that prevents the toner and the like from leaking out. Next, a separating method of the developing agent recycling apparatus that separates a magnetic toner from other foreign substances will be described. The conveying screw 24' in the conveying path 24 extends in the vicinity of an inner surface (surface D of Fig. 3) of the frame 17 in parallel with the sleeve 18. The conveying path 24 has an opening on the sleeve 18 side. Thus, the residue (foreign substances such as magnetic toner and paper powder) that have been conveyed by the conveying screw 24' are attracted to the front surface of the sleeve 18 by the magnetic force of the magnet 18' disposed in the sleeve 18. (At this point, the foreign substances such as non-magnetic paper powder are mixed with the magnetic toner. Thus, the foreign substances are attracted to the front surface of the sleeve 18 along with the magnetic toner.) The thickness of the residue adhered to the front surface of the sleeve 18 is restricted by the doctor blade 25. As the sleeve 18 is rotated, the residue is conveyed to an opposed region of the sleeves 19 and 18 where the toner is separated from the foreign substances (namely, the region where the magnetic force of the sleeve 19 satisfactorily affects the residue). The residue conveyed to the separating portion opposed to the sleeve 19 is effectively attracted to the sleeve 19 by converged magnetic lines of force extending from a magnetic pole S18 to a magnetic pole N19. The magnetic forces of the magnetic poles N19 and S18 at the separating portion have the relation N19 > S18. Thus, the toner is strongly attracted upwardly through the openings of the mesh 20 by the magnetic pole N19. The mesh 20 has openings that are several times larger than the diameter of toner particles. (When a toner with average particle diameter of 5 µm to 20 µm is used, the mesh should preferably have openings of 37.5 µm sq (#400) to 50 µm sq (#100).) Thus, the toner easily passes through the mesh 20, whereas paper powder that is attracted do not pass through the mesh 20. Thus, since the paper powder is restricted by the surface of the sleeve 18, they drop to the sleeve 18 by their dead weight. The paper powder is held by the sleeve 18. Thus, the foreign substances such as paper powder are conveyed to a non-magnetic contacting member 28 along with the residual toner that has not been attracted to the sleeve 19 and the residual foreign substances that have not floated. The non-magnetic contacting member 28 scrapes off these foreign substances from the front surface of the sleeve 18. The non-magnetic contacting member 28 is lightly contacted with the sleeve 18. Thus, the non-magnetic contacting member 28 can scrape off foreign substances such as paper powder that adhere to the sleeve 18 with a weak force. However, since the toner that has not been removed by the separating portion is attracted to the sleeve by the magnetic force, it cannot be scraped off by the non-magnetic contacting member 28. As the sleeve is rotated, the same separating process is repeated. Thus, most of the developing agent is not collected into a collecting portion 29. In other words, the collecting portion 29 collects only foreign substances most of which are non-magnetic substances. Since the sleeve 19, which is a developing agent attracting member, is disposed upstream of the filter 20 in the gravity working direction, the foreign substances such as paper powder drop from the filter by their dead weight. Thus, the developing agent recycling apparatus according to this embodiment can properly separate a developing agent from other foreign substances without occurrences of clogging of the filter. In this embodiment, the mesh 20 is vibrated by a cam 22 connected to a drive motor 23 through a supporting member 21 that holds the mesh 20. The frequency and amplitude of the vibrations are preferably 50 Hz or higher and 0.2 to 4 mm, respectively. Some toner particles contained in the residue may be aggregated. The aggregated toner particles may adhere to the openings of the mesh 20. In particular, when relative humidity is high, the toner particles tend to be aggregated and adhere to the openings of the mesh 20. Thus, the mesh 20 may be clogged. When the aggregated toner particles that adhere to the mesh 20 are vibrated, they are destroyed, thereby preventing the mesh 20 from being clogged (see Fig. 4). When a magnetic force that attracts the developing agent is much stronger than the dead weight of the developing particles, they are easily attracted to the sleeve 19 disposed upstream of the mesh 20 in the gravity working direction. In this embodiment, since the magnetic toner is conveyed from the downstream side to upstream side in the gravity working direction and separated from non-magnetic substances, the non-magnetic substances (foreign substances) separated from the magnetic toner adhere to the lower surface of the mesh. Thus, the non-magnetic substances drop by their dead weight and the vibrations applied to the mesh. Thus, the magnetic toner can be effectively separated from the foreign substances. In addition, the mesh can be continuously prevented from clogging. As the sleeve 19 is rotated, the magnetic toner that has been separated from the paper powder and attracted to the sleeve 19 is conveyed to the scrape-off blade 26. The scraped magnetic toner is conveyed by the screw 27 to the outside of the developing agent recycling apparatus. The magnetic toner separated is conveyed to a developing system by a conveying unit (not shown) and then used for the developing process. Fig. 5 shows a developing agent recycling apparatus according to a second embodiment of the present invention. In Fig. 5, reference numerals 31 and 32 are magnet rollers that are disposed so that opposite magnetic poles are opposed at their opposed portions. The magnetic poles (N1 and S1) of the magnet roller 31 and the magnetic poles (N2 and S2) of the magnet rollers 32 have the relations of N1 > S2 and S1 > N2. The magnetic poles of the magnet rollers 31 and 32 are disposed with predetermined angles and rotated by a drive source (not shown) at the same speed so that the magnetic poles of the opposed magnet rollers 31 and 32 are opposite. Next, the operation of the developing agent recycling apparatus according to the second embodiment will be described. After residue is removed from the photosensitive drum, the thickness of the residue that adheres to the surface of the magnet roller 32 is restricted by a doctor blade 25. The residue is conveyed to the separating portion. A magnetic toner is effectively attracted to a magnet roller 31 by converged magnetic lines of force generated by the opposed magnetic poles. Since the magnetic forces N1 and S1 on the upper side are larger than the magnetic forces N2 and S2 on the lower side, the magnetic toner is attracted upwardly through openings of a mesh 20 to magnetic poles N1 and S1. As with the manner of the first embodiment, the magnetic toner is separated from foreign substances by the mesh 20. In addition, a scrape-off roller 33 that is made of a magnetic material is contacted with the magnet roller 31. Thus, the magnetic toner that adheres to the front surface of the magnet roller 31 is attracted to the scrape-off roller 33. The magnetic toner is scraped off by a scrape-off blade 26 contacted with the scrape-off roller 33. The magnetic toner separated from the foreign substances is conveyed to the outside of the developing agent recycling apparatus by a conveying screw 27. The foreign substances such as paper powder that have dropped from the openings of the mesh 20 are held on the magnet roller 32. The foreign substances are conveyed as the magnet roller 32 is rotated. The non-magnetic foreign substances are scraped off by a protruding portion 17b to a collecting portion 29. At this point, the magnetic toner that has not passed through the openings of the mesh 20 and has been held on the magnet roller 32 is conveyed to a downward section, not scraped off by a cleaning brush 34. As the sleeve is rotated, the same separating process is repeated. Thus, most of the magnetic toner is not collected into a collecting portion 29. In other words, the collecting portion 29 collects only foreign substances most of which are non-magnetic substances. In the second embodiment, a filter was disposed in a gravity working direction (in other words, nearly in parallel with the installation plane of the image forming apparatus). However, it should be appreciated that the present invention is not limited to such a construction. Instead, as long as foreign substances such as paper powder drop from the filter by their dead weight, the installation angle of the filter is not limited to that in the second embodiment. Next, a third embodiment of the present invention will be described. Fig. 6 is a sectional view schematically showing an image forming apparatus with a developing agent recycling apparatus according to the third embodiment. As shown in Fig. 6, reference numeral 101 is a document table glass on which an original document is placed. Reference numeral 103 is a lamp that illuminates the original document (exposing lamp). Reference numerals 105, 107, and 109 are scanning and reflecting mirrors (scanning mirrors) that change optical paths of rays of light reflected from the original document. Reference numeral 111 is a lens with focusing and zooming functions. Reference numeral 113 is a fourth reflecting mirror (scanning mirror) that changes an optical path. Reference numeral 115 is a motor that drives an optical system. Reference numerals 117, 119, and 121 are sensors. Reference numeral 131 is a photosensitive drum. Reference numeral 133 is a main motor that drives the photosensitive drum 131. Reference numeral 135 is a high voltage unit. Reference numeral 137 is a blank exposing unit. Reference numeral 139 is a developing unit. Reference numeral 141 is a transferring charger. Reference numeral 143 is a separating charger. Reference numeral 145 is a cleaning unit. Reference numeral 151 is a upper cassette. Reference numeral 153 is a lower cassette. Reference numeral 171 is a manual feeder. Reference numerals 155 and 157 are paper feed rollers. Reference numeral 159 is a resist roller. Reference numeral 161 is a conveying belt that conveys a recording paper that has recorded an image to a fixing section. Reference numeral 163 is a fixing unit that thermally fixes the image to the recording paper. The front surface of the photosensitive drum 131 is coated with a photoconductor and a seamless photosensitive member made of a conductor. The photosensitive drum 131 is rotated in the direction of arrow of Fig. 6. The main motor 133 is activated according to the operation of a copy start key. After predetermined rotation control process and voltage control process (pre-processes) of the drum 131 are completed, the original document placed on the original document table glass 101 is illuminated by the lamp 103 incorporated with the first scanning mirror 105. The rays of light reflected from the original document are focused on the drum 131 through the first scanning mirror 105, the second scanning mirror 107, the third scanning mirror 109, the lens 111, and the fourth scanning mirror 113. The drum 131 is corona charged by the primary charger 135. Thereafter, an image (original document image) illuminated by the lamp 103 is slit exposed and then a latent image is formed on the drum 131 by a known Carlson process. Thereafter, the static latent image on the photosensitive drum 131 is developed by a developing roller 140 of the developing unit 139. Thus, a toner image is visualized and transferred to a transferring paper by the transferring charger 141. In other words, a transferring paper in the upper cassette 151, the lower cassette 153, or the manual feeder 171 is conveyed to the inside of the image forming apparatus by the paper feed roller 155 or 157. The leading edge of the latent image is matched with the leading edge of the transferring paper. Thereafter, the transferring paper is conveyed between the transferring charger 141 and the drum 131 and then unloaded to the outside of the image forming apparatus. After the latent image is transferred to the transferring paper, the drum 131 is still rotated and the surface thereof is cleaned by the cleaning unit 145 that is constructed of a cleaning roller and an elastic blade. The collected residue is conveyed by a conveying screw 148 and guided to a developing agent recycling apparatus 200 shown in Fig. 7. Reference numeral 148 is a screw that conveys the residue from the cleaning unit to the developing agent recycling apparatus 200. The screw 148 conveys the residue from the rear side to front side shown in the drawing. Reference numeral 201 is a first magnetic field generating member that attracts a magnetic toner and foreign substances mixed with a magnetic toner by a magnetic force of a fixed magnet disposed in the sleeve. Thereafter, the sleeve is rotated in the direction of arrow of the drawing and thereby these toner and foreign substances mixed therewith are conveyed to a position opposed to a second magnetic field generating member 202. For example, the distance between the first and second sleeves is approximately 3 mm. The magnetic flux density of an N pole at an opposed position of the first sleeve is 750 Gauss. The magnetic flux density of an S pole at an opposed position of the second sleeve is 1000 Gauss. A mesh filter 203 made of a non-magnetic material such as phosphor bronze is disposed at a nearly center position between the first and second sleeves and perpendicular to the installation plane of the image forming apparatus (namely, in parallel with the gravity working direction). The mesh density of the filter is preferably five to fifty times as large as the particle diameter of toner (thus, the filter preferably has 200 to 300 meshes). The mesh filter can be vibrated. For example, as shown in Fig. 8, the mesh filter is disposed between frames 350 and 351. A leaf spring 352 is contacted with a part of the mesh filter. An elastic leaf cam 354 is connected to a rotating shaft 353 of a motor. As the leaf cam is rotated, the leaf spring is vibrated and thereby the mesh filter is vibrated. The residue held on the first sleeve is attracted at an opposed position of the second sleeve by a magnetic field generated by the first and second sleeves. At this point, the magnetic field causes the magnetic toner contained in the residue to move from the first sleeve to the second sleeve. Thus, the magnetic toner, which moves from the first sleeve to the second sleeve, is held on the surface of the second sleeve through the mesh of the filter. At this point, since part of paper powder contained in the residue is mixed with a toner, this paper powder tends to move from the first sleeve to the second sleeve. However, since the particle size of the paper powder is much larger than the particle size of the toner, the mesh of the filter prevents the paper powder from moving from the first sleeve to the second sleeve. Most toner, which is mixed with the paper powder and which causes the paper powder to move from the first sleeve to the second sleeve, passes through the mesh of the filter. Thus, when the paper powder arrives at the mesh of the filter, it loses the moving force. In addition, the mesh of the filter is disposed between the first sleeve and the second sleeve nearly in parallel with the gravity working direction. Thus, when the paper powder arrives at the mesh of the filter, it drops from the surface of the mesh by its dead weight. Consequently, the developing agent recycling apparatus according to the third embodiment can separate the magnetic toner from the foreign substances such as paper powder without occurrences of clogging of the mesh of the filter. In this embodiment, the mesh of the filter is vibrated. Since the mesh filter is vibrated, aggregated toner in the vicinity of the mesh filter is loosened and thereby smoothly passes through the mesh filter. In addition, with the vibrations, the paper powder tends to easily drop from the mesh filter. The paper powder that has dropped from the mesh filter is conveyed to a residue collecting portion by a screw 206. Fig. 9 shows the relation between vibrations and amount of toner that passes through the mesh filter per predetermined time unit (toner passing efficiency). Fig. 10 shows the relation between the amount of toner that passes through the mesh filter per predetermined time unit (toner passing efficiency) and the number of papers copied both in the case that the mesh filter is vibrated at 100 Hz and in the case that the mesh filter is not vibrated. In Fig. 10, line m represents the case that the mesh filter is vibrated and line n represents the case that the mesh filter is not vibrated. As clear from Figs. 9 and 10, the vibrations cause the toner smoothly to pass through the mesh filter without occurrences of clogging thereof. The toner that has moved to the second sleeve is conveyed to a scraper 204 as the second sleeve is rotated in the direction of arrow of the drawing. The scraper 204 scrapes off the toner from the second sleeve. The scraped toner is conveyed to a developing agent hopper or a developing unit by a screw 205. Thus, the toner is reused. Fig. 11 shows a fourth embodiment of the present invention. In Fig. 11, reference numeral 148 is a screw that conveys residue collected from a cleaner to a developing agent recycling unit. The collected toner is attracted to a sleeve 601 by for example an N pole of a magnet (as a magnetic field generating means) fixed in the sleeve 601. The sleeve 601 is rotated in the direction of arrow of Fig. 11 so as to convey the collected toner. Reference numeral 203 is a non-magnetic mesh filter. Reference numeral 602 is a magnet roller with a plurality of magnetic poles (for example, eight magnetic poles). The magnet roller is rotated in the direction of arrow of Fig. 11. When the magnetic poles of the opposed magnet sleeves 601 and 602 become opposite each other (in other words, when an N pole of the magnet sleeve 601 is opposed to an S pole of the magnet roller 602), the collected toner is attracted to the magnet roller 602. Thus, the toner passes through the mesh filter and then adheres to the magnet roller 602. As the magnet roller 602 is rotated, the same magnetic poles of the magnet sleeve 601 and the magnet roller 602 are opposed. Thereby, the toner is not (or less) attracted to the magnet roller 602. Thus, the collected toner is not present in the vicinity of the mesh filter. The effect of repetition of this process is similar to the effect of the vibrations of the mesh filter. Non-magnetic residue do not pass through the mesh filter, but drops therefrom. This residue is conveyed to a residue collecting portion by a conveying screw 606 along the mesh filter. On the other hand, the toner that adheres to the magnet roller 602 is conveyed to a scraper 604 in the reverse direction of the arrow shown in the drawing. The scraper 604 scrapes off the toner. The scraped toner is conveyed to a hopper or a developing unit by a conveying screw 605. Thus, the toner is reused. It should be noted that the rotating magnet roller may attract residue and causes it to move in the mesh direction and the sleeve may attract the toner through the mesh. The pair of magnetic field generating means may be formed of a pair of rotating magnet rollers. In the third embodiment, a mesh filter was vibrated by a rotating cam. However, as shown in Fig. 12, an ultrasonic vibrator may be disposed at the mesh filter so as to vibrate it. Next, an embodiment where part of foreign substances such as paper powder are removed by a first magnetic field generating means will be described. Fig. 13 shows a fifth embodiment. In Fig. 13, reference numeral 148 is a screw that conveys residue that has removed from the surface of a photosensitive member from the rear side to front side shown in the drawing. Reference numeral 201 is a first magnet sleeve. The collected toner is attracted by a magnetic force of a magnet disposed in the sleeve. Thereafter, the sleeve is rotated in the direction of arrow shown in the drawing. The thickness of the collected toner is restricted to for example 300 µm by a blade 210. Thus, paper powder and the like are scraped off by the blade 210. In addition, the blade 210 limits the amount of collected toner to be conveyed to a position opposed to a second magnet sleeve 202. Thus, when a large amount of collected toner is conveyed to a mesh filter, it is clogged therewith. However, since the blade 210 limits the amount of toner, the mesh filter is prevented from being clogged with the toner. The distance between the first and second sleeves is approximately 3 mm. The magnetic flux density of an N pole at an opposed position of the first sleeve is 750 Gauss. The magnetic flux density of an S pole at an opposed position of the second sleeve is 1000 Gauss. A mesh filter 203 made of a non-magnetic material such as phosphor bronze is disposed at a nearly center position between the first and second sleeves. The mesh density of the filter is preferably five to fifty times as large as the particle diameter of the toner (thus, the mesh filter preferably has 200 to 300 meshes). The mesh filter can be vibrated. For example, as with the manner of the first embodiment, the mesh filter is disposed between frames 350 and 351. A leaf spring 352 is contacted with a part of the mesh filter. An elastic leaf cam 354 is connected to a rotating shaft 353 of a motor. As the leaf cam is rotated, the leaf spring is vibrated and thereby the mesh filter is vibrated. The collected toner held on the first sleeve is attracted at a position opposed to the second sleeve. By a converged magnetic field of the second sleeve, part of toner is attracted to the second sleeve through the mesh filter. When the mesh filter is vibrated, aggregated toner in the vicinity of the mesh filter becomes loose. Thus, the toner smoothly passes through the mesh filter. On the other hand, when the blade is rotated, paper powder and the like collected by the blade portion are scraped off by a cleaning member such as a felt 211. The scraped substances drop to a conveying screw 206. The conveying screw 206 conveys the substances to a residue collecting portion. Fig. 14 shows the relation between the number of papers copied and amount of toner that passes through the mesh filter per predetermined time unit (toner passing efficiency) both in the case that the blade is used and in the case that the blade is not used. The case that the blade is used is represented by a solid line. The case that the blade is not used is represented by a dotted line. As is clear from Fig. 14, in the case that the blade is used, after a large number of papers have been copied, toner effectively and stably passes through the mesh filter. The toner that has passed through the mesh filter is conveyed to a scraper 204 as the second sleeve is rotated in the direction of arrow shown in the drawing. The scraper 204 scrapes off the toner from the second sleeve. The scraped toner is conveyed to a developing agent hopper or a developing unit by a screw 205. Thus, the toner is reused. Fig. 15 shows a sixth embodiment of the present invention. In the sixth embodiment, as with the manner of the above-described embodiment, residue is attracted to a first magnet sleeve. Thereafter, the sleeve is rotated in the direction of arrow shown in Fig. 15. Reference numeral 215 is a brush roll that is spaced apart from the sleeve by around 0.5 mm and is rotated in the counterclockwise direction. The brush collects paper powder and the like. In addition, the brush roll limits the amount of toner conveyed to a position opposed to a second magnet sleeve 202. Thus, a large amount of toner is not conveyed to a mesh filter portion, thereby preventing it from being clogged with the toner. Thereafter, as with the manner of the third embodiment, the toner that has passed through the mesh filter is reused. On the other hand, paper powder and the like that have been collected by the brush roll is removed by an elastic plate 216. Thus, these substances drop downward to a conveying screw 206. The conveying screw 206 conveys these substances to a residue collecting portion. When a roller is used instead of the brush roll, although the efficiency of removing paper dust and the like is degraded, the similar effect can be obtained. In a seventh embodiment, the thickness of collected toner layer is restricted with a blade in the same construction as the fifth embodiment. As shown in Fig. 16, since the edge portion of the blade is formed in a saw shape, the efficiency of removing paper powder is improved. In addition, this construction can prevent the blade portion from being clogged with paper powder and the like. Thus, the collected toner can be stably conveyed to a mesh filter portion. The mesh filter is vertically disposed. The magnetic force generating means causes the toner to horizontally pass through the mesh filter. In addition, the mesh filter is vibrated. Thus, aggregated toner in the vicinity of the mesh filter can become loose. The thickness of toner layer in the mesh filter portion is restricted. Moreover, paper powder and the like are pre-treated. Thus, the efficiency for passing the toner to the mesh filter is improved. Moreover, even if a large number of toner is collected, it can be effectively reused. As is clear from the first to seventh embodiments, the installation angle α of the filter should be in the range from 0°, which is an angle in parallel with the installation plane of the image forming apparatus as with the first and second embodiments, to 90°, which is an angle perpendicular to the installation plane thereof as with the third to seventh embodiments. In other words, when the angle to a plane perpendicular to gravity working direction is α = 0°, the installation angle of the filter should be in the range of 0° ≤ α ≤ 90°. As described in the first to seventh embodiments, when an attracting member is disposed upstream of the filter in the gravity working direction, the filter can be prevented from being clogged and thereby the maintenance sessions of the apparatus can be reduced. In the following embodiment, while an image forming apparatus is stopped, a mesh filter can be prevented from being clogged. Next, an eighth embodiment of the present invention will be described. For simplicity, the same portion as the above-described embodiments are denoted by the same reference numerals. In a developing agent recycling apparatus according to the eighth embodiment, relative positions of magnetic poles of sleeves 18 and 19 that are opposed with a mesh 20 therebetween so as to prevent the mesh 20 from being clogged while a copy operation is stopped or the power of the image forming apparatus is turned off. Next, with reference to Figs. 2, 17, and 18, the eighth embodiment of the present invention will be described. Shaft ends 19a and 20a that are rotatably connected to the sleeves 18 and 19 protrude from a frame 17a of a developing agent recycling apparatus 17. The shaft ends 19a and 20a are formed in a D cut shape. The D cut shaped shaft ends 19a and 20a are connected to respective ends of magnetic pole aligning plates 31 and 32, respectively. The other end of the magnetic pole aligning plate 31 is fixed to the frame 17a with a machine screw. While the developing agent recycling apparatus is separating a toner from paper powder, the magnetic pole position of the magnet disposed in the sleeve 19 is fixed as shown in Fig. 2. The other end of the magnetic pole aligning plate 32 connected to a shaft fixed to a magnet 18' is connected to a shaft 33. The shaft 33 is fit to an oval hole 35 defined at one end of a lever 34. The lever 34 has a rotating fulcrum 36 fixed to the frame 17a. The other end of the lever 34 is fit to an iron core 39 of a solenoid 38 with a pin 37. One end of a resilient spring 40 is hooked in the vicinity of the oval hole 35 at one end of the lever 34. The other end of the resilient spring 40 is hooked to a bend portion 42 of a solenoid support table 41. Thus, the magnet disposed in the sleeve 18 is resiliently rotated in the counterclockwise direction by the resilient force of the resilient spring 40. In addition, the magnet of the sleeve 18 that is resiliently rotated is contacted with a bend portion 43 of the solenoid support table 41. Thus, the magnetic pole position is fixed. The rotations of the sleeves 18 and 19 are transferred by a drive source (not shown) through gears and the like. Thus, in the developing agent recycling apparatus according to the eighth embodiment, regardless of whether or not a copy operation is being performed, the magnet 19' is always oriented in the same direction. In other words, as shown in Fig. 2, an N pole of the magnet 19' is always opposed to the mesh 20. On the other hand, a magnetic pole of the magnet 18' that is opposed to the mesh 20 is changed depending on whether or not the copy operation is being performed. In other words, as shown in Fig. 17, while the copy operation is being performed, the solenoid 38 is energized and thereby the iron core 39 is attracted. Thus, the magnetic pole position of the magnet disposed in the sleeve 18 is fixed in a developing agent recycling position as shown in Fig. 2. The solenoid 38 is adjustably mounted on the support table 41 so that the magnetic pole position of the magnet 18' is precisely set when the iron core 39 is attracted. As shown in Fig. 18, after the copy operation is completed, the solenoid 38 is deenergized and the lever 34 is rotated in the counterclockwise direction by the resilient force of the resilient spring 40. In addition, the magnetic pole aligning plate 32 is rotated in this direction and thereby the lever 34 is contacted with the bend portion 43 of the solenoid support table 41 at a position where a magnetic pole N18 of the magnet 18' is opposed to a magnetic pole N19 of the magnet of the sleeve 19. Thus, the magnetic pole position of the magnet 18 is fixed. In other words, while the copy operation is not being performed, the magnetic poles N18 and N19 are opposed with the mesh 20. Thus, magnetic toner does not move from the magnetic pole N18 to the magnetic pole N19. With the above-described construction and operation, while the copy operation is stopped or the main switch of the image forming apparatus is turned off, developing agent in the vicinity of the sleeves 18 and 19 can be prevented from being aggregated. In the eighth embodiment, when the solenoid 38 was deenergized, the magnet was rotated in the same direction as the sleeve 18. However, it should be noted that the rotating direction of the magnet may be the same as that of the sleeve 18. In this case, while the copy operation is stopped, foreign substances such as paper powder (other than developing agent) that are present between the doctor blade 25 and the sleeve 18 are removed. Since the thickness of the developing agent on the surface of the sleeve 18 is not changed, the conveying force of the developing agent to the mesh portion 20 is not lowered. In the eighth embodiment, it should be appreciated that the magnet disposed in the sleeve 19 may be rotated instead of the magnet 18' disposed in the sleeve 18. As shown in Fig. 19, the present invention may be applied to a developing agent recycling apparatus where the mesh 20 that serves as a mesh filter is vertically disposed and sleeves 18 and 19 with respective magnets that serve as magnetic field generating means are disposed at opposed positions with the mesh 20 therebetween. Next, with reference to Fig. 20, a ninth embodiment of the present invention will be described. Fig. 20 is a sectional view showing a construction of a separating apparatus according to the ninth embodiment of the present invention. For simplicity, the same portions as the above-described embodiments are denoted by the same reference numerals. In Fig. 20, reference numerals 51 and 52 are magnet rollers that serve as magnetic force generating means and that are disposed at opposed positions of a separating portion so that the magnetic poles of the opposed magnet rollers become opposite. The magnet poles (N11 and S11) of the magnet roller 51 and the magnet poles (N21 and S21) of the magnet roller 52 have the relation of N11 > S21 and S11 > N21. The magnet poles are disposed at predetermined angles. The magnet rollers 51 and 52 are rotated at a same speed by a drive source (that will be described later) so that the magnetic poles of the opposed magnet rollers at the separating portion become opposite. Next, the operation of the developing agent recycling apparatus will be described. A developing agent held on the magnet roller 52 is scraped off by a doctor blade 25 so as to restrict the thickness of the developing agent layer on the magnet roller 52. The developing agent held on the magnet roller 52 is conveyed to the separating portion. At the separating portion, the developing agent is effectively attracted by converged magnetic lines of force. Since the magnetic force of the magnetic poles N11 and S11 of the upper magnet roller 51 is larger than that of the magnetic poles N21 and S21 of the lower magnet roller 52, the developing agent is strongly attracted to the magnetic poles N11 and S11 and moved upward through a mesh 20. The developing agent is separated from the foreign substances by the mesh 20. The magnet roller 51 is contacted with a scrap-off roller 53 made of a magnetic material and is rotated. The developing agent that has been separated is temporarily attracted and transferred to the scrape-off roller 53. The developing agent is scraped off by a scrape-off blade 54 contacted with the scrape-off roller 53. The developing agent separated from the foreign substances are conveyed by a conveying screw 27' to the outside of the developing agent reproducing apparatus 17. The residual foreign substances and residual developing agent are conveyed to a downstream section by the magnet roller 52. Foreign substances are collected by a cleaning brush 55 made of a non-magnetic material. The foreign substances are scraped off by a protruding portion 17a1 to a collecting portion 29. Since the residual developing agent has a magnetic force, it is still attracted by the magnet roller 52. Thus, the residual developing agent is conveyed to the downstream section, rather than being collected by the cleaning brush 55. Thus, the developing agent separating operation is performed for the residual developing agent. Consequently, most of developing agent is not collected to the collecting portion. Only foreign substances made of non-magnetic materials are collected to the collecting portion 29. The developing agent recycling apparatus 17 has a construction where the relative positions of magnetic poles of the magnet rollers 51 and 52 opposed with the mesh 20 therebetween can be changed so as to prevent the mesh 20 from being clogged when the copy operation is stopped or the power of the image forming apparatus is turned off. This construction will be described with reference to Figs. 21 to 23. Figs. 21 and 22 are sectional views showing the construction of a magnetic pole position changing mechanism. Fig. 23 is a block diagram showing a control system of the developing agent recycling apparatus. A gear 56 is engaged with a shaft end 51a of a magnet roller 51 outside a frame 17a of the developing agent recycling apparatus 17. The magnet roller 51 is rotated by a drive source (not shown) through a gear 57 rotatably connected on the frame 17a. A gear 58 that is engaged with the gear 56 is disposed at a shaft end 52a of the magnet roller 52. A one-way clutch 59 is disposed between the shaft end 52a of the magnet roller 52 and the gear 58. The one-way clutch 59 limits the rotating direction in one way. With the one-way clutch 59, when the developing agent recycling apparatus is operated, in the case that the gear 58 is rotated in the direction of arrow shown in the drawing, the magnet roller 52 is rotated in the same direction. Since the magnet rollers 51 and 52 should be rotated in phase so that the magnetic poles at the opposed positions of the magnet rollers 51 and 52 are always opposite, the number of teeth of the gear 56 is the same as that of the gear 58. To assemble or disassemble the magnet rollers 51, and 52 and the gears 56 and 58 for repair or maintenance, magnetic pole aligning marks may be placed on the magnet rollers 51 and 52 for initial phase adjustment. While the copy operation is being performed, the magnet rollers 51 and 52 are rotated in the respective directions of arrows shown in the drawing so as to separate an image forming agent from foreign substances such as paper powder. After the copy operation is completed, the magnet rollers 51 and 52 are rotated in these directions by the respective drive shafts. When a flag 60 fixed on a side surface of the drive gear 56 blocks a photo sensor 62 disposed on the frame 17a of the developing agent recycling apparatus 17 through a support plate 61, a signal that is output from the photo sensor 62 causes the rotations of the magnet rollers 51 and 52 to stop so that the magnet pole N11 and the magnet pole S21 are opposed at the separating portion (see Fig. 20). Thereafter, a microprocessor unit (MPU) that controls the developing agent recycling apparatus causes the drive source to rotate the magnet rollers 51 and 52 in the reverse directions of arrows shown in the drawing. When a flag 63 disposed on a side surface of the drive gear 56 blocks a photo sensor 64 disposed through the support plate 61, a signal that is output from the photo sensor 64 causes the magnet rollers 51 and 52 to stop. Since the one-way clutch 59 is disposed between the magnet roller 52 and the gear 58, while the gear is rotated in the reverse direction of arrow shown in the drawing, the magnet roller 52 is not rotated. Thus, when the flag 63 blocks the photo sensor 64, the magnet roller 51 is stopped so that the magnetic pole S11 thereof and the magnetic pole S21 of the magnet roller 52 are opposed at the separating portion. As shown in Fig. 23, the control system controls the developing agent recycling apparatus as follows. When signals that are output from the photo sensors 62 and 64 are sent to the microprocessor unit (MPU) 66 through an interface 65, a motor driver 68 is driven through an output interface 67 corresponding to the signals so as to drive a drive motor 69 that rotates the magnet rollers. In the developing agent recycling apparatus according to the ninth embodiment, when the same magnetic poles of the magnet rollers 51 and 52 are opposed at the separating portion, the magnet rollers 51 and 52 are rotated by their repelling forces. To prevent the opposed magnetic poles from being moved, a weak current may be supplied to a motor that is the drive source of the magnet rollers 51 and 52. With the holding force of the motor, the magnet rollers 51 and 52 may be prevented from being rotated. Unlike with the driving and transferring mechanism of the above-described developing agent recycling apparatus, the one-way clutch 59 may be disposed between the magnet roller 51 and the gear 56. Although the present invention has been shown and described with respect to a best mode embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof may be made therein without departing from the scope of the present invention as claimed.

Claims: A developing agent recycling device for recycling a magnetic developing agent from a mixture of the magnetic developing agent and foreign substances, said recycling device having an attracting member for attracting said magnetic developing agent and a filter having a plurality of holes for preventing other than said magnetic developing agent from passing, said filter being disposed in a region where said magnetic developing agent is moved by said attracting member, wherein said attracting member has a first magnetic field generating member disposed upstream of said filter in a toner moving direction for attracting said magnetic developing agent and a second magnetic field generating member disposed downstream of said filter in the toner moving direction for attracting said developing agent, wherein said mixture is attracted to said first magnetic field generating member, moved to a position opposed to said second magnetic field generating member, and attracted toward said second magnetic field generating member, and wherein said first magnetic field generating member and said second magnetic field generating member are disposed so that opposite magnetic poles are opposed and that the magnetic flux density of said second magnetic field generating member is larger than the magnetic flux density of said first magnetic field generating member. The developing agent recycling device as set forth in claim 1, wherein said filter has a mesh. The developing agent recycling device as set forth in claim 2, wherein the density of said mesh is in the range from #400 to #100. The developing agent recycling device as set forth in claim 1, wherein said filter has a plane surface and an installation angle α satisfies the relation from 0° ≤ α ≤ 90° where an angle perpendicular to a gravity working direction is α = 0. An image forming apparatus for forming an image of a developing agent on a recording member, comprising: an image carrier; image forming means for forming the image on said image carrier; cleaning means for removing a residue from said image carrier after the image has been transferred to said recording member; and a developing agent recycling device according to one of the preceding claims.

Inventors: KATSUMI TORU, KOIKE MICHIRO, SAITO HIRONOBU, TAKEDA ATSUSHI, KATSUMI, TORU, KOIKE, MICHIRO, SAITO, HIRONOBU, TAKEDA, ATSUSHI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1994
Main classification: G03G15
IPC codes: G03G15, G03G21